Abstract: In order to avoid damage to the inner walls of the arc furnace (1) and a reduction of the electric power when material (5) to be melted has been partly burned down in an arc furnace (1), additives (10) are fed to the filling opening of a hollow electrode (7) by means of a loose-material conveyor (25) during this critical melting phase. An arc (6) between the hollow electrode (7) and a melt (4) in the arc furnace (1) is thereby shortened. A loose-material container (9) is arranged at the end of the loose-material conveyor (25) at a distance from the electrode and can easily be separated from the hollow electrode (7) in order to permit the tilting of the arc furnace (1) to empty out the melt (4). Problematic waste materials which are to be disposed of, such as for example filter dust, can be added to the additives (10).

Abstract: The furnace vessel for a DC arc furnace has a thermostable wall which preferably consists, in the region situated above the slag line (S), of a plurality of water-cooled wall segments (1) made from steel. These wall segments are fastened to a support structure (13-18). At least one of the wall segments (3) consists of nonmagnetic steel or copper and is preferably arranged on the side of the furnace vessel (5) opposite the power supply device (7). In this way, the influence of the high-current lines which extend below or beside the furnace vessel and cause a deflection of the arc can be compensated.The effect of this nonmagnetic wall segment can be partially or virtually entirely cancelled by a trimming plate (19) which is detachably fastened from the outside to the nonmagnetic wall segment (3), in order in this way to achieve optimum trimming of the deflection of the arc.

Abstract: A method and a d.c. arc furnace for thermal treatment of an ash, wherein reducing conditions are established within a closed and sealed furnace, the ash is supplied via a channel arranged in an electrode which extends towards a metal melt in a furnace shell and provides an arc extending toward the metal melt, the ash being fed from the open free end of the electrode through the arc, any slag and/or the metal melt, whereby the ash is rapidly heated under reducing conditions to a temperature of 1350.degree. C. to 1750.degree. C.

Abstract: To improve operation, particularly to allow more universal use, in which both liquid and solid crude metal, especially iron can be refined in only one reactor vessel, a reactor vessel (1) is of converter-like design with a relatively large space above a melt (7) and with slag (8) lying above said melt. For the removal of slag (8) via a closable slag channel (18'), the meltdown apparatus can be rotated about a center of rotation (20) through .+-.8.degree.. For the complete removal of the melt (7) via a closable melt channel (17') in the bottom region of the meltdown apparatus, the latter can be rotated about a center of rotation (19) through .+-.30.sup.. A magnetic coil (16) fed with direct current and arranged around the meltdown apparatus (1) serves for the magnetic damping of movements of melt (7) and/or slag (8) inside the meltdown apparatus. In the converter mode, a graphite electrode (5) used in the arc mode is replaced by a gas supply conduit, through which oxygen is then supplied under pressure.

Abstract: In order to reduce the power loss of a direct current arc furnace the furnace vessel is only partially cooled in the region situated above the melting zone. A first cooling device is provided on a top edge of the vessel. A second cooling device is provided at the height of a slag line. The region of a vessel wall situated therebetween and facing the interior of the vessel above the slag line consists essentially of refractory material.

Abstract: A choke coil comprises mutually similar flat bars which are electrically connected at the corners. Each coil winding comprises an integral number of mutually similar flat bars which in each case lie on top of one another on contact areas at the corners so as to overlap over a large area. Insulating plates and/or insulating layers having a size approximately equal to the contact area are provided between two adjacent windings at the corners. The stack formed in this way is held together exclusively by means of a clamping device comprising clamping elements which do not cut or pierce the flat bars. A choke constructed in this manner is simple and economical to manufacture can be cooled well and can be produced in virtually any size.

Abstract: In a direct-current arc furnace having a bottom contact (3) which has a large area, electromagnetically produced bath agitations are influenced by an electromagnet (9) disposed underneath the vessel bottom (4) such that the natural flow in the melt bath, caused by the current flow in the melt, is reversed in direction. In this way the stability of the bottom electrode (3) is substantially increased. The electromagnet (9) is preferably integrated into the electric supply system of the furnace and serves as a smoothing choke.

Abstract: In direct-current arc furnace the arc is deflected in a direction away from the current supply means (19) through the action of the high-current lines (18) extending under the furnace vessel. This leads to the thermal overloading of a part of the furnace vessel walls. If the high-current lines (18a) are for the major part laid in a plane above the furnace bottom, on or below the furnace platform (20), and are taken downwards to the connection fittings (10) on the furnace bottom only on the side of the furnace vessel (1) opposite the current supply means, the arc will again burn symmetrically.

Abstract: A direct current arc furnace has a furnace vessel which is surrounded by a metal shell having at least one electrode connected as a cathode, and at least one bottom contact. The bottom of the furnace consists of a lining layer which possesses electrically conducting bricks or the like, which lining layer lies on a contact plate covering most of the bottom. The contact plate forms the bottom contact connected as the anode and lies on a bottom plate. The bottom plate is equipped with a plurality of connection fittings which pass through openings in the bottom plate and are connected via electric wires to a current supplying device provided next to the furnace. For the internal deflection of the arc, at least one section of the lining layer is composed of a material which possesses a lower electrical conductivity than the lining layer in another section which is circumferentially spaced from the one section so as to form circumferentially spaced zones of varying conductivity.

Abstract: In a direct-current electric-arc furnace, the bottom contact, that is the hearth electrode, must be insulated from the metallic shell of the furnace vessel by insulating material. For this purpose, the bottom plate carrying the bottom contact essentially forms the bottom of the furnace vessel. This bottom contact, with an insulating material, or a material which is at least a poor electrical conductor, inbetween, rests on a part, projecting radially inward, of the metallic vessel shell.

Abstract: In a direct-current arc furnace having a bottom electrode (2), electromagnetically and/or chemically induced bath agitations are substantially eliminated by an electromagnet (9) arranged under the vessel bottom (7). In this way the stability of the bottom electrode (2) is considerably increased. The electromagnet (9) is preferably integrated into the electrical supply of the furnace and serves as a smoothing choke.

Abstract: A new method of making an electrically conductive hearth in a d.c. furnace is effected by first heating bricks such as magnesite-graphite bricks and the like, from their new commercially available form to high temperatures decresing the normal resistivity of the bricks and thereafter laying the bricks to form the hearth from top to bottom with the heat treated bricks.

Abstract: Electrically conductive refractory bricks, containing particles (e.g. flakes) of graphite or other electrically conductive material are pressed into the desired final shape but include a plurality of passages, none of which passes completely through the brick. The passages each extend substantially perpendicularly to the predominant direction of the conducting particles.

Abstract: A DC arc furnace having an electrically conductive hearth adapted to contain a melt, and at least one arcing electrode above the hearth and adapted to form a heating arc with the melt when the hearth and electrode are supplied with DC power; the hearth having a wear lining directly contacted by the melt and formed by refractory material through which electrical conductors extend from the bottom of the wear lining to its top. A metal plate under the wear lining electrically connects with the conductors and is supported by one or more electrically non-conductive layers of refractory. Power connection to the wear lining is via the plate and a connection with the periphery of the plate.

Abstract: A DC arc furnace comprising a furnace vessel having a hearth and a side wall extending upwardly from the hearth, conductive means for conducting DC through the hearth from its outside to a melt in the hearth, an arcing electrode, a substantially horizontal arm having a holder holding the electrode substantially vertically above the hearth, a substantially vertical mast from which the arm extends, and means for connecting DC positively to the conductive means and negatively to the electrode so as to form an arc between the electrode and the melt and producing an arc flare to which the side wall is exposed; wherein the improvement comprises means for connecting the arm to the mast so as to permit the arm to be adjustably moved longitudinally to different positions and means for mounting the mast so it can be adjustably rotated to different positions about its axis, whereby the electrode and its arc can be located at different positions horizontally to the side wall.

Abstract: A DC arc furnace including a hearth adapted to contain a melt and having a melt electrode which is only effective when covered by the melt, an enclosure for the hearth including a roof over the hearth, at least one arcing electrode depending downwardly through the roof and adapted to initially melt a charge of solid metal on the hearth and thereafter the resulting melt, and at least one starting electrode through which electric power is transmitted to the charge of solid metal until it is melted down by the arcing electrode to enough melt to cover the melt electrode; the starting electrode or electrodes depending downwardly through the roof at a position horizontally offset from the arcing electrode and being adapted to be moved downwardly so as to press on the charge of solid scrap on the hearth until the charge is melted down by the arcing electrode so as to cover the melt electrode and thereafter to be moved upwardly free from the charge.

Abstract: A DC arc furnace having a vertical arcing electrode adapted to be connected with a negative current lead and a hearth adapted to contain a melt below the electrode and having a hearth electrode, the hearth electrode extending laterally from the axis of the arcing electrode symmetrically with respect to the axis and having a plurality of electrical connections extending to the outside of the hearth and spaced laterally from the arcing electrode's axis symmetrically with respect to the axis, the connections being adapted for connection with a positive current lead and application of DC to the electrodes powering an arc between the arcing electrode and melt; wherein the improvement comprises a positive current lead below the bottom of the hearth and having an upper end positioned on the arcing electrode's axis below the hearth's bottom and extending from the positive current lead's upper end vertically downwardly on the axis to a low position where the magnetic field of the positive current lead cannot appreciab

Abstract: A DC arc furnace has an electrically conductive hearth adapted to contain a melt, and at least one arcing electrode above the hearth and adapted to form a heating arc with the melt when the hearth and electrode are supplied with DC power. The hearth has a wear lining directly contacted by the melt through which electrical conductors extend from the bottom of the wear lining to its top. Layers of electrically conductive bricks are under the wear lining and have a top layer electrically connecting with the electrical conductors, and a melt plate under the layers of the electrically conductive bricks is connected to DC power. The layers of conductive bricks have a bottom layer in electrical connection with the melt plate. The improvement comprises a layer of mixed bricks between the top and bottom layers of the electrically conductive bricks and formed by alternating electrically conductive and non-conductive bricks.

Abstract: A metallurgical ladle furnace has a ladle for containing the melt, an arcing electrode positioned on the ladle's axis, and a melt electrode in the ladle's lower portion and substantially symmetric with respect to the arcing electrode. DC power applied to the electrodes results in an arc between the arcing electrode and the melt for heating the melt and incidentally causing the melt to stir in vertical directions, the melt moving downwardly in the middle below the arc, upwardly along the walls of the melt and inwardly towards the arc. A DC powered coil surrounds the ladle horizontally at half the ladle's height or higher, around the upper portions of the melt. The field of this coil in cooperation with a DC flow in the melt caused by the current flow between the electrodes, provides a substantially tangential stirring force on the melt which is in addition to the stirring force of the electrode current in the melt.

Abstract: The present invention relates to a method and a device for operating a DC arc furnace with a bottom in the furnace vat consisting of rammed compound (8) or bricks with metallic elements (7) which are in electrically conductive contact, directly or via electrically conductive bricks (10) such as carbon bricks, with a hearth connection (11). The method is characterized in that, after melting and possibly further treatment of a charge (15), when tapping said melt such a quantity thereof is left that said remainder, the sump (17), may serve as part of a starting electrode for the next melting operation.